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Abstract Two form ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) genes from the obligately autotrophic, marine hydrogen oxidizer Hydrogenovibrio marinus were sequenced. The deduced amino acid sequences of both RuBisCOs revealed that they are similar to those of sulfur oxidizers (Thiobacillus) and a purple sulfur bacterium (Chromatium vinosum). According to the 16S rRNA gene sequences, H. marinus is also affiliated with these microorganisms, members of Thiomicrospira being the closest relatives. Sequence similarities of the 16S rRNA genes and of the RuBisCO genes among these γ-Proteobacteria suggest a common autotrophic ancestry. An ancestor of purple sulfur bacteria might be a common root of H. marinus and related sulfur oxidizers.

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Abstract The expression of the Arabidopsis heat shock protein (HSP) 18.2 promoter-β-d-glucuronidase (GUS) chimera gene was investigated in transgenic Nicotiana plumbaginifolia plants during the recovery phase at normal temperatures (20–22 °C) after a heat shock (HS) treatment. GUS activity increased during the recovery phase after HS at 42 °C for 2 h, and maximal GUS activity was observed after 12 h at normal temperatures, at levels 50–100 times higher than the activity immediately after HS. After HS at 44 °C, little GUS activity was observed during the first 20–24 h at normal temperatures, but the activity increased gradually thereafter, to reach a maximum at 40–50 h. After HS at 45 °C, no GUS activity was observed throughout the experimental period. RT-PCR analysis showed that GUS mRNA remained for 10 h after a 2-h HS at 42 °C and for 40 h after a 2-h HS at 44 °C. These findings demonstrate that brief HS treatment, especially at a sublethal temperature, induces a long-term accumulation of HSP-GUS mRNA during the recovery phase.